Composition and process for surface treatment of aluminum and its alloys

ABSTRACT

An aqueous liquid surface treatment composition having a pH value not more than 6.5 and containing phosphoric acid ions, condensed phosphoric acid ions, an oxidizing agent, and a water-soluble polymer consisting, except for end groups, of polymer units expressed by formula (I), in a weight ratio of 0.1 to 30:0.1 to 10:0.1 to 10:0.1 to 20 respectively, when brought into contact with an aluminiferous metal surface, rapidly forms on the surface a conversion coating that has good corrosion resistance and adhesion to subsequently applied organic coatings such as paint and is less easily damaged by mechanical stresses than prior art conversion coatings. ##STR1##

TECHNICAL FIELD

The present invention relates to a novel composition and method for thesurface treatment of aluminum and its alloys, such as aluminum-manganesealloys, aluminum-magnesium alloys, and aluminum-silicon alloys, thatcontain at least 45% by weight of aluminum, all of these being jointlyhereinafter briefly designated as "aluminiferous metals", in which thesurface of an aluminiferous metal is provided with better corrosionresistance and adhesion to paint or synthetic resin film before saidsurface is painted or is laminated to a synthetic resin film. One fieldin which the present invention may be particularly effectively appliedis the surface treatment of aluminiferous coils.

BACKGROUND ART

Chromate treatments are presently being used for the most part in theindustrial surface treatment of aluminum coils. Typical examples ofchromate treatments include chromic acid chromate conversion treatmentsand phosphoric acid chromate conversion treatments. Chromic acidchromate conversion treatment solutions were put to practical use around1950 and are still widely used for fin members and the like in heatexchangers. This chemical conversion treatment solution consistsprimarily of chromic acid (CrO₃) and hydrofluoric acid (HF), with apromoter added, and forms a film containing some hexavalent chromium.Phosphoric acid chromate conversion treatment solutions are based on theinvention in U.S. Pat. No. 2,438,877 from 1945. This chemical conversiontreatment solution contains chromic acid (CrO₃), phosphoric acid (H₃PO₄), and hydrofluoric acid (HF). The film that is formed consistsprimarily of hydrated chromium phosphate (CrPO₄.4H₂ O). Since the filmdoes not contain hexavalent chromium, it is widely used at present forthe paint undercoating treatment of beverage can bodies, particularlydrawn and ironed aluminum cans and lids. However, in the interests ofenvironmental protection, a need has arisen for surface treatmentsolutions which contain no chromium. In recent years, the painting orlamination following such surface treatment has been followed by anincreasingly wide range of shaping processes, with the need forincreasingly stringent levels of processing, but films made frominorganic systems such as chromate suffer from problems; e.g., the filmis broken when bent sharply, preventing adequate performance from beingrealized, and the like. There is thus strong demand for the developmentof a technique for forming a flexible film with better corrosionresistance and/or adhesion in articles of manufacture that are shapedafter the conversion coating is formed.

Treatment solutions or methods intended to provide the surface ofaluminiferous metals with corrosion resistance and paint adhesion usinga water-soluble resin have been proposed in Japanese Laid-Open PatentApplications 61-91369, 1-172406, 1-177379, 1-177380, 2-608, 2-609, andothers. In these conventional treatment methods, the metal surface istreated with a solution containing a derivative of a polyhydric phenolcompound. Problems in these conventional methods, however, are that itis difficult to form a sufficiently stable film in a short period oftime on the surface of aluminiferous metal materials, and adequatecorrosion resistance cannot be obtained.

DISCLOSURE OF THE INVENTION Problems to Be Solved by the Invention

The present invention is intended to remedy the aforementioned drawbacksof the conventional technology, and more specifically is intended tooffer a novel composition and method for surface treating aluminiferousmetals, which allow the surface of an aluminiferous metal to be providedin a short period of time with better corrosion resistance and paint orlaminated film adhesion, without the use of chromium, and which alsoallow a film with better workability to be formed.

SUMMARY OF THE INVENTION

It has been found that an aqueous liquid surface treatment compositioncontaining phosphoric acid ions, condensed phosphoric acid ions, anoxidizer, and a water-soluble polymer with a specific structure and thathas a pH within a specific range forms a film with better corrosionresistance and paint or laminated film adhesion, as well as betterworkability, when a surface of an aluminiferous metal is brought intocontact with such a surface treatment composition.

More particularly, a composition according to the invention for thesurface treatment of an aluminiferous metal comprises, preferablyconsists essentially of, or more preferably consists of, water and:

(A) a component of ions of orthophosphoric acid;

(B) a component of ions of condensed phosphoric acid(s);

(C) a component of oxidizing agent; and

(D) a component of molecules of water-soluble polymer and/or oligomersconforming, except for end groups, to the following general formula (I):##STR2## in which each of X¹ and X² independently of each other andindependently from one unit of the polymer, said unit being defined asrepresented by a modification of formula (I) above in which the squarebrackets and the subscript n are omitted, to another unit of the polymerrepresents a hydrogen atom, a C₁ to C₅ alkyl group, or a C₁ to C₅hydroxyalkyl group; each of Y¹ and Y² independently of one another andindependently for each unit of the polymer represents a hydrogen atom ora moiety "Z" which conforms to one of the following general formulas(II) and (III): ##STR3## in which each of R¹, R², R³, R⁴, and R⁵ in eachof general formulas (II) and (III) independently represents a C₁ to C₁₀alkyl group or a C₁ to C₁₀ hydroxyalkyl group; one moiety "Z" may beidentical to or may differ from any other moiety "Z" in the polymermolecule, so long as each "Z" conforms to one of the general formulas(II) and (III); and n represents a positive integer, which may be thesame as or different from the value of n for any other polymer molecule;in addition, in component (D) as a whole: the average value for thenumber of Z moieties substituted on each phenyl ring in the polymermolecule¹, which may be referred to hereinafter as "the average valuefor Z moiety substitution", is from 0.2 to 1.0; the average value of n,which may be referred to hereinafter as "the average degree ofpolymerization", is from 2 to 50, and, because it is an average, neednot be an integer;

    ((1×10)+(0×10'))/20=0.5

and, optionally, one or both of the following components:

(E) a component of aluminum sequestering agent that is not part of anyof the previously recited components; and

(F) a component of antifoam agent that is not part of any of thepreviously recited components,

and in the composition as a whole, the aforementioned phosphoric acidions (A), condensed phosphoric acid ions (B), oxidizing agent (C), andwater-soluble polymer (D) are present in a weight ratio (A):(B):(C):(D)of 0.1 to 30:0.1 to 10:0.1 to 10:0.1 to 20. A composition according tothe invention may be immediately suitable for use as such in treatingaluminiferous metal, in which instance it is called a workingcomposition, or it may be suitable for diluting with additional water toform a working composition, in which instance it is called a concentratecomposition. Some compositions are suitable for both purposes.

A process for the surface treatment of an aluminiferous metal accordingto the present invention is characterized by the fact that an aqueoussurface treatment solution which contains the aforementioned surfacetreatment composition pertaining to the present invention and which hasa pH value no more than 6.5 is brought into contact with the surface ofan aluminiferous metal, preferably for a total of 1 to 60 seconds, andthe surface which has thus contacted preferably is then rinsed withwater, and then is dried and preferably heated.

DETAILED DESCRIPTION OF THE INVENTION, INCLUDING PREFERRED EMBODIMENTS

Orthophosphoric acid, having the chemical formula H₃ PO₄ and hereinusually designated simply as "phosphoric acid" unless the contextrequires differentiating it from other phosphoric acids, and any watersoluble salt or acid salt of orthophosphoric acid that does not actadversely to the objects of the invention may be used as a source ofcomponent (A) of a composition according to the invention as definedabove, and any such salt is to be understood, for the purpose of thepreferences indicated below, as contributing its full stoichiometricequivalent as orthophosphate ions (i.e., PO₄ ⁻³) to the concentrationthereof in any composition according to the invention, irrespective ofthe actual degree of ionization that may prevail in the composition. Thephosphoric acid ions content ranges from 0.1 to 30 weight parts, andpreferably 0.5 to 5 weight parts, per 0.1 to 20 weight parts ofwater-soluble polymer (D) in the aforementioned ratio. A phosphoric acidions content of less than 0.1 weight part in the aforementioned blendratio often results in inadequate reactivity between the surfacetreatment solution and the surface of the metal substrate being coated,as well as in an inadequately formed film. More than 30 weight parts inthis ratio does not harm formation of a favorable conversion coating butis uneconomical because of the higher cost of the treatment solution andlack of any offsetting benefit compared with compositions containingsomewhat less of this component.

Similarly, one or two or more types selected from among pyrophosphoricacid, tripolyphosphoric acid and tetrapolyphosphoric acid, and the saltsof all of these acids, can be used to provide the condensed phosphoricacid ions in a water-based composition of this invention, but theinvention is not limited to the use of these materials. Any watersoluble source of any phosphate anions that contain at least two atomsof phosphorus each may be used, and is to be understood for the purposesof the preferences below as supplying its full stoichiometric equivalentas condensed phosphate anions to the composition used according to theinvention, irrespective of the actual degree of ionization that existsin the composition. For example, pyrophosphoric acid (H₄ P₂ O₇), sodiumpyrophosphate (Na₄ P₂ O₇) and like compounds can be used to providepyrophosphate ions. In a surface treatment composition according to thepresent invention, the content of the condensed phosphoric acid ionscomponent (B) ranges from 0.1 to 10 weight parts, and preferably 0.5 to3.0 weight parts, per 0.1 to 20 weight parts of water-soluble polymer(D). A condensed phosphoric acid ions content of less than 0.1 weightpart in the aforementioned ratio normally results in a surface treatmentsolution with weak etching action, preventing a film from beingadequately formed. A content of more than 10 weight parts usuallyresults in a surface treatment solution with etching action that is toostrong, which inhibits the film-forming reaction.

In a surface treatment composition according to the present invention,the oxidizing agent preferably comprises, more preferably consistsessentially of, or still more preferably consists of one or moresubstances selected from the group consisting of hydrogen peroxide,chlorates, and nitrites; the use of hydrogen peroxide is most preferred.The content of oxidizing agent component (C) in the aforementioned ratiofor the surface treatment composition according to the present inventionranges from 0.1 to 10 weight parts, and preferably 2 to 5 weight parts,per 0.1 to 20 weight parts of water-soluble polymer component (D). Anoxidizing agent content of less than 0.1 weight part usually results ina treatment solution with weak etching action, preventing an adequatefilm from being formed. More than 10 weight parts usually results in atreatment solution with etching action that is too strong, whichinhibits the film-forming reaction.

The water-soluble polymer used in the present invention is awater-soluble polymer (a term intended herein to include oligomers) thathas an average degree of polymerization of 2 to 50, or preferably of 2to 20, and that contains, preferably consists essentially of, or morepreferably consists of (except for end groups) polymer units asdescribed above in connection with general formula (I).

When the alkyl or hydroxyalkyl groups represented by X¹ and X² ingeneral formula (I) have 6 or more carbon atoms, the resulting polymerbecomes bulky, usually causing steric hindrance and preventing a compactfilm with good corrosion resistance from being obtained.

When the average value for Z substitutions is less than 0.2, theresulting polymer normally has poor water solubility, and the resultingsurface treatment composition stability is usually inadequate. When theaverage value for Z moiety substitution is more than 1.0, and thuscontains a substantial fraction of benzene rings substituted by two ormore Z groups, the polymer usually has such a high water solubility thata composition containing it as component (D) has great difficulty informing a satisfactorily protective surface film.

The alkyl or hydroxyalkyl groups expressed by R¹, R², R³, R⁴, and R⁵ ingeneral formulas (II) and (III) have 1 to 10 carbon atoms. A number ofcarbon atoms of 11 or more usually results in a polymer molecule that istoo bulky, leading to a film with poor density and insufficientcorrosion resistance.

In a surface treatment composition according to the present invention,the content of the water-soluble polymer component (D), in terms of theaforementioned ratios to other components, is 0.1 to 20 weight parts,and preferably 0.5 to 5 weight parts, per 0.1 to 30 weight parts ofphosphoric acid ions (A). When this ratio is less than 0.1 weight part,it is difficult to form a film on the surface of aluminiferous metalswith the surface treatment composition, whereas more than 20 weightparts in this ratio is uneconomical because of the higher cost of theresulting surface treatment and lack of any substantial improvement overthe results achieved with a composition according to the inventioncontaining 20 or fewer parts in this ratio.

Although not narrowly limited, the pH of a working surface treatmentcomposition according to the present invention is preferably no morethan 6.5, and even more preferably is between 2.0 and 6.5. When the pHof the surface treatment composition is higher than 6.5, the polymer offormula (I) in the resulting surface treatment composition tends toprecipitate, impairing the treatment composition stability and its uselife. When the pH is lower than 2.0, the etching action of the surfacetreatment composition on the surface of the metal material is verystrong, making it difficult to form a surface film. The pH of thesurface treatment composition can be adjusted using an acid such asphosphoric acid, nitric acid, and hydrochloric acid, or an alkali suchas sodium hydroxide, sodium carbonate, and ammonium hydroxide.Hydrofluoric acid may be used to adjust the pH when wastewater disposalis not a problem.

In a surface treatment method according to the present invention, theaforementioned surface treatment solution preferably has a pH of 2.0 to6.5 and contains from 1 to 30 grams per liter (hereinafter usuallyabbreviated as "g/l") of phosphoric acid ions, from 0.1 to 10 g/l ofcondensed phosphoric acid ions, from 0.1 to 10 g/l of oxidizing agent,and from 0.1 to 20 g/l of water-soluble polymer component (D) asdescribed above. When the concentration of phosphoric acid ions in asurface treatment composition according to the invention is lower than0.1 g/l, a surface film is usually inadequately formed, whereas morethan 30 g/l is uneconomical because of higher costs. When theconcentration of the condensed phosphoric acid ions is lower than 0.1g/l, the etching action of the resulting surface treatment compositionis usually too weak, and a surface film is inadequately formed, whereasmore than 10 g/l results in a surface treatment composition with etchingproperties that are so strong that the film-forming reaction ishindered. When the oxidizing agent concentration is lower than 0.1 g/l,the etching action of the resulting surface treatment composition isweak, usually preventing the formation of an adequate film, whereas morethan 10 g/l results in a surface treatment composition with etchingaction that is too high, which hinders the film-forming reaction. Whenthe concentration of the water-soluble polymer component (D) is lowerthan 0.1 g/l, the resulting surface treatment composition usually hasinadequate film formability, whereas more than 20 g/l is economicallydisadvantageous because of higher costs.

When aluminum ions that have eluted from the aluminiferous metal becomemixed with the surface treatment composition, the water-soluble polymer(D) and the metal ions sometimes form a complex and produceprecipitation. In such instances, an aluminum sequestering agent shouldbe added to the surface treatment composition. Examples of usefulaluminum sequestering agents include, but are not limited to, ethylenediamine tetra-acetic acid, 1,2-cyclohexane-diamine tetra-acetic acid,triethanolamine, gluconic acid, heptogluconic acid, oxalic acid,tartaric acid, malic acid, and organophosphonic acids. When the use ofhydrofluoric acid poses no problems for wastewater treatment, it may beused as a sequestering agent.

In a method of the present invention, a working surface treatmentcomposition as described above is brought into contact, preferably for atotal of 1 to 60 seconds and independently preferably at a temperaturewithin a range from 30 to 65° C., with a surface of an aluminiferousmetal. The film formed on the surface of the metal material is thenpreferably rinsed with water, and thereafter preferably is heated anddried. Contact between the aluminiferous metal and a working compositionmay be established by any convenient method, among which immersion ofthe substrate in a bath of the working composition and spraying theworking composition on the metal are most common. A contact time of lessthan 1 second usually results in inadequate formation of acorrosion-resistant film, whereas a contact time of more than 60 secondsyields no greater benefits and thus leads to less operationalefficiency.

When a spray treatment is used, the surface treatment compositionsometimes foams and thus causes problems in the film that is formed.Although the presence or absence of foaming and the extent of suchfoaming depends largely on the spraying equipment and conditions, adefoaming agent should be added to the surface treatment compositionwhen foaming is not suitably avoided by modification of the sprayingequipment and conditions. The type of defoaming agent, the amount used,and so forth are not narrowly limited, but the adhesion between theresulting film and the paint or laminated film should not becompromised.

The film formed on the surface of the aluminiferous metal in a processaccording to the invention is believed to be a film of anorganic-inorganic composite consisting primarily of phosphates andwater-soluble polymer (resin) (D). The metal substrate is etched by theions of the phosphoric acid and condensed phosphoric acid, at which timethe pH becomes elevated in some areas at the interface, resulting in theprecipitation of phosphates on the surface. The amino groups (includedin the groups Z) of the water-soluble polymer (D) have chelating action,and are believed to form a type of coordination compound with theregenerated surface of the metal substrate produced by the etching.Although the organic-inorganic composite film is basically formed as aresult of the two aforementioned actions, the additional presence of thecondensed phosphoric acid ions in the surface treatment compositionappears to allow some water-soluble polymer-metal coordinationcompound(s) to be more readily formed, thereby allowing a stableorganic-inorganic complex film to be formed on the metal surface withina wide pH range.

After a coating film has been formed in a process according to theinvention, the film can be and preferably is heated to allow the polymerfrom component (D) of the working composition according to the inventionthat was used, and that was incorporated into the coating film formed onthe surface, to undergo further polymerization on the surface. At leastone minute at 200° C. (in the normal ambient natural atmosphere) issufficient for the heating conditions.

A preferred expanded treatment process step sequence, using a surfacetreatment composition according to the present invention, is outlinedbelow.

(1) Surface cleaning/degreasing (any acidic, alkaline, or solvent type);

(2) Rinsing with water;

(3) Surface treatment (by method of the present invention);

(4) Rinsing with water;

(5) Deionized water rinsing;

(6) Heating and drying;

(7) Painting or film lamination.

Before the method of the present invention is implemented, the surfaceof the metal material is preferably cleaned so that it is degreased ofoil such as rolling oil or the like remaining on the surface of thealuminiferous metal that is being treated. No particular restrictionsare imposed on the type of degreasing agent or the degreasing methodused in this step. The degreased material is then preferably rinsed withwater. The rinsing is intended to remove the degreasing composition fromthe surface; therefore, any rinsing method may be used, provided thatthe degreasing composition is removed from the surface. The surfacetreatment of the method according to the present invention is thenimplemented. The surface of the aluminiferous metal being treated is thepreferably further rinsed with water. This rinsing is intended to removethe surface treatment composition, so any rinsing method may be used,provided that the unreacted surface treatment composition is removedfrom the surface. The heating and drying are intended to dry off therinsing water, with no narrow restrictions imposed on the method, dryingtemperature, drying time, or the like, although hot air drying or thelike is generally useful for industrial purposes. The surface of thealuminiferous metal that has been surface treated is then painted orlaminated with film. The coating formed by a method according to thepresent invention has good adhesion to paint or laminated films. Sincethe coating formed by means of the present invention is also flexible,it also has excellent performance after processing such as folding ordrawing.

The aluminiferous metals used in the method according to the presentinvention include forms such as sheets, bars, tubes, wires, and thelike. No restrictions whatever are imposed on the dimensions andconfiguration of the metal, although the method according to the presentinvention is especially effective when used on aluminiferous metalcoils.

The present invention is described in further detail below withreference to specific working and comparison examples.

EXAMPLES AND COMPARISON EXAMPLES

Methods of Evaluation

(1) Corrosion Resistance

The corrosion resistance of aluminum materials (resistance to darkeningfrom boiling water) was evaluated by the following test: Treatedaluminum objects were bent into the shape of a U around a round bar witha diameter of 1 millimeter (hereinafter usually abbreviated as "mm");these were immersed for 30 minutes in boiling tap water; and the degreeof discoloration (darkening) in the bent parts was visually assessed. Nodarkening was rated as "◯", partial darkening was rated as "Δ", andtotal darkening was rated as "×".

(2) Paint Adhesion

Paint adhesion was tested in the following manner: Polyvinyl chloridepaint for cans was painted to a thickness of between 5 and 10micrometers (hereinafter usually abbreviated as "μm") on the surface oftreated aluminum, followed by 1 minute of baking at 260° C.; the sampleswere cut into rectangles 5×150 mm; the painted surfaces were thermallybonded via a polyamide film to form test pieces; the bonded surfaceswere separated by the 180 degree peel test method; and the peel strengthwas evaluated at that time. The greater the peel strength, the betterthe paint adhesion. In general, a peel strength of 4.0 kilograms-force(hereinafter usually abbreviated as "kgf") or more per 5 mm of width isconsidered excellent for practical purposes.

(3) Wastewater Disposability

Used surface treatment composition waste was diluted twenty-fold withwater, and the concentration of hexavalent chromium in the thus formedcomposition was measured. For the purposes of environmental protection,no chromium should be detected.

Example 1

An aluminum-magnesium alloy sheet (alloy according to JapaneseIndustrial Standard, hereinafter usually abbreviated as "JIS", A5182)was degreased by spraying with a 2% aqueous solution of an alkalinedegreaser (trade name: FINECLEANER® 4377K, by Nihon Parkerizing) for 5seconds at 60° C., and was then rinsed clean with water. The sheet wasthen sprayed for 3 seconds at 60° C. with Surface Treatment Composition1 having the ingredients noted below, with the balance being water; itwas then rinsed with tap water, then sprayed and washed for 10 secondswith deionized water having a specific resistivity of at least 3,000,000ohm-centimeters, and was then dried for 2 minutes in a hot air dryingfurnace at 80° C.

    ______________________________________                                        Surface Treatment Composition 1                                               ______________________________________                                        75% Phosphoric acid (i.e., H.sub.3 PO.sub.4)                                                        10.0 g/l (PO.sub.4.sup.3- :7.2 g/l)                     Sodium pyrophosphate (i.e., Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O)                                   3.0 g/l (P.sub.2 O.sub.7.sup.4- :1.2 g/l)               31% Hydrogen peroxide in water                                                                      10.0 g/l (H.sub.2 O.sub.2 :3.1 g/l)                     Polymer (1) - solids part                                                                           2.0 g/l                                                 pH 4.0 (Adjusted with sodium hydroxide)                                       ______________________________________                                    

Water Soluble Polymer (1) was according to general formula (I) when: theaverage value of n=5; each of X¹ and X² represents a hydrogen atom; eachof Y¹ and Y² represents a --CH₂ N(CH₃)₂ moiety or hydrogen atom; and theaverage Z moiety substitution number=0.50

Example 2

Aluminum alloy materials were degreased and rinsed clean in the samemanner as in Example 1, and they were then treated by immersion for 10seconds at 40° C. using Surface Treatment Composition 2 having theingredients shown below, with the balance being water. This treatmentwas followed by rinsing and drying under the same conditions as inExample 1.

    ______________________________________                                        Surface Treatment Composition 2                                               ______________________________________                                        75% Phosphoric acid (i.e., H.sub.3 PO.sub.4)                                                        10.0 g/l (PO.sub.4.sup.3- :7.2 g/l)                     Sodium pyrophosphate (i.e., Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O)                                   3.0 g/l (P.sub.2 O.sub.7.sup.4- :1.2 g/l)               31% Hydrogen peroxide in water                                                                      15.0 g/l (H.sub.2 O.sub.2 :4.6 g/l)                     Polymer (2) - solids part                                                                           0.4 g/l                                                 pH 3.0 (Adjusted with sodium carbonate)                                       ______________________________________                                    

Water soluble polymer (2) was according to general formula (I) when: theaverage value of n=5; each of X¹ and X² =a --C₂ H₅ moiety; each of Y¹and Y² =a --CH₂ N(CH₂ CH₂ OH)₂ moiety or a hydrogen atom; and theaverage value for Z moiety substitution=0.25.

Example 3

Aluminum alloy sheets were degreased and rinsed clean in the same manneras in Example 1, were then spray treated for 1 second at 65° C. usingSurface Treatment Composition 3 containing the ingredients shown below,with the balance being water, then rinsed and dried under the sameconditions as in Example 1.

    ______________________________________                                        Surface Treatment Composition 3                                               ______________________________________                                        75% Phosphoric acid (i.e., H.sub.3 PO.sub.4)                                                        20.0 g/l (PO.sub.4.sup.3- :14.4 g/l)                    Sodium pyrophosphate (i.e., Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O)                                   6.0 g/l (P.sub.2 O.sub.7.sup.4- :2.4 g/l)               31% Hydrogen Peroxide in water                                                                      15.0 g/l (H.sub.2 O.sub.2 :4.6 g/l)                     Polymer (3) - solids part                                                                           8.0 g/l                                                 pH 4.0 (Adjusted with sodium hydroxide)                                       ______________________________________                                    

Water soluble polymer (3) was according to general formula (I) when: theaverage value of n=15; each of X¹ and X² =a --C₂ H₅ moiety; each of Y¹and Y² =a --CH₂ N(CH₂ CH₂ OH)₂ moiety or a hydrogen atom; and theaverage value for Z moiety substitution=1.0.

Example 4

Aluminum alloy sheets were degreased and rinsed clean in the same manneras in Example 1, were then spray treated for 30 seconds at 40° C. usingSurface Treatment Composition 4 containing the ingredients shown below,with the balance being water, then rinsed and dried under the sameconditions as in Example 1.

    ______________________________________                                        Surface Treatment Composition 4                                               ______________________________________                                        75% Phosphoric acid (i.e., H.sub.3 PO.sub.4)                                                        20.0 g/l (PO.sub.4.sup.3- :14.4 g/l)                    Sodium tripolyphosphate (i.e., Na.sub.5 P.sub.3 O.sub.10)                                           1.2 g/l (P.sub.3 O.sub.10.sup.4- :0.8 g/l)              43% Sodium chlorate in water                                                                        10.0 g/l (NaClO.sub.3 :4.3 g/l)                         Polymer (4) - solids part                                                                           1.0 g/l                                                 pH 4.0 (Adjusted with aqueous ammonia)                                        ______________________________________                                    

Water soluble polymer (4) was according to general formula (I) when: theaverage value of n=15; each of X¹ and X² represents a hydrogen atom;each of Y¹ and Y² represents a --CH₂ N(CH₂ OH)₂ moiety or a hydrogenatom; and the average value for Z moiety substitution=0.50

Example 5

Aluminum alloy sheets were degreased and rinsed clean in the same manneras in Example 1, were then spray treated for 5 seconds at 50° C. usingSurface Treatment Composition 5 containing the ingredients shown below,with the balance being water, then rinsed and dried under the sameconditions as in Example 1.

    ______________________________________                                        Surface Treatment Composition 5                                               ______________________________________                                        75% Phosphoric acid (i.e., H.sub.3 PO.sub.4)                                                        20.0 g/l (PO.sub.4.sup.3- :14.4 g/l)                    Pyrophosphoric acid (i.e., H.sub.4 P.sub.2 O.sub.7)                                                 1.0 g/l (P.sub.2 O.sub.7.sup.4- :0.98 g/l)              31% Hydrogen Peroxide in water                                                                      5.0 g/l (H.sub.2 O.sub.2 :1.6 g/l)                      Polymer (5) - solids part                                                                           1.0 g/l                                                 pH 3.5 (Adjusted with aqueous ammonia)                                        ______________________________________                                    

Water soluble polymer (5) was according to general formula (I) when: theaverage value of n=20; each of X¹ and X² =a hydrogen atom; each of Y¹and Y² =a --CH₂ N(CH₂ CH₂ CH₂ OH)₂ moiety or a hydrogen atom; and theaverage value for Z moiety substitution=0.75.

Comparative Example 1

Aluminum alloy sheets were degreased and rinsed clean in the same manneras in Example 1, and they were then spray treated for 5 seconds at 50°C. using Surface Treatment Composition C1 having the ingredients setforth below, with the balance being water. This treatment was followedby rinsing and drying under the same conditions as in Example 1.

    ______________________________________                                        Surface Treatment Composition C1 - with no                                    condensed phosphoric acid ions or oxidizing agent                             ______________________________________                                        75% Phosphoric acid (i.e., H.sub.3 PO.sub.4)                                                        20.0 g/l (PO.sub.4.sup.3- :14.4 g/l)                    Polymer (6) - solids part                                                                           1.0 g/l                                                 pH 3.5 (Adjusted with aqueous ammonia)                                        ______________________________________                                    

Water soluble polymer (6) was according to general formula (I) when: theaverage value of n=10; each of X¹ and X² =a hydrogen atom; each of Y¹and Y² =a --CH₂ N(CH₂ CH₂ CH₂ OH)₂ moiety or a hydrogen atom; and theaverage value for Z moiety substitution=0.75.

Comparative Example 2

Aluminum alloy sheets were degreased and rinsed clean in the same manneras in Example 1, were then spray treated for 2 seconds at 50 CC using a5% aqueous solution of a commercially available phosphoric acid chromatetype of chemical conversion composition (tradename: ALCHROME® K 702, byNihon Parkerizing). The treatment was followed by rinsing and dryingunder the same conditions as in Example 1.

Comparative Example 3

Aluminum alloy sheets were degreased and rinsed clean in the same manneras in Example 1, were then spray treated for 10 seconds at 50° C. usinga 6% aqueous solution of a commercially available zirconium phosphatetype of chemical conversion composition (tradename: AEROSIL™ 404, byNihon Parkerizing). The treatment was followed by rinsing and dryingunder the same conditions as in Example 1.

Table 1 shows the results obtained in the evaluations of the above notedExamples 1 through 5 and Comparative Examples 1 through 3.

                  TABLE 1                                                         ______________________________________                                                         Paint Adhesion                                                                           Wastewater                                                Corrosion                                                                              (Peel Strength,                                                                          Disposability                                             Resistance                                                                             kgf/5 mm)  (Cr.sup.+6, g/l)                                  ______________________________________                                        Example 1 0          4.0        none detected                                 Example 2 0          4.0        none detected                                 Example 3 0          4.0        none detected                                 Example 4 0          4.0        none detected                                 Example 5 0          4.0        none detected                                 Comparative                                                                             x          1.5        none detected                                 Example 1                                                                     Comparative                                                                             x          4.0        0.2                                           Example 2                                                                     Comparative                                                                             x          1.5        none detected                                 Example 3                                                                     ______________________________________                                    

It is apparent from the results in Table 1 that Examples 1 through 5which used a method according to the present invention had bettercorrosion resistance, adhesion, and wastewater disposability.

In Comparative Example 1, the surface treatment composition contained nocondensed phosphoric acid ions or oxidizing agent, resulting in a filmwith inadequate corrosion resistance and paint adhesion. In ComparativeExamples 2 and 3, conventional surface treatment compositions were used,resulting in films with low corrosion resistance. In Comparative Example2, the wastewater contained hexavalent chromium, while in ComparativeExample 3, the paint adhesion was poor.

Benefits of the Invention

It is apparent from the aforementioned description that the surfacetreatment composition and method according to the present inventionallow a chemical conversion film with better corrosion resistance andpaint adhesion to be formed on the surfaces of aluminiferous metalsbefore they are painted. The surface treatment composition and methodaccording to the present invention are non-chromium and non-fluorinetypes, and have the exceptional merit of alleviating the burden ofwastewater disposal.

The invention claimed is:
 1. A liquid composition of matter suitable foruse as such, after dilution with water, or both as such and afterdilution with water for the surface treatment of aluminiferous metals,said composition comprising water and:(A) a component of ions oforthophosphoric acid; (B) a component of ions of condensed phosphoricacid(s); (C) a component of oxidizing agent; and (D) a component ofmolecules of water-soluble polymers, oligomers, or both polymers andoligomers, each of said molecules conforming, except for end groups, tothe following general formula (I): ##STR4## in which each of X¹ and X²independently of each other and independently from one unit of themolecule, said unit being defined as represented by a modification offormula (I) above in which the square brackets and the subscript n areomitted, to another unit of the molecule represents a hydrogen atom, aC₁ to C₅ alkyl group, or a C₁ to C₅ hydroxyalkyl group; each of Y¹ andY² independently of one another and independently for each unit of thepolymer represents a hydrogen atom or a moiety "Z" which conforms to oneof the following general formulas (II) and (III): ##STR5## in which eachof R¹, R², R³, R⁴, and R⁵ in each of general formulas (II) and (III)independently represents a C₁ to C₁₀ alkyl group or a C₁ to C₁₀hydroxyalkyl group; one moiety "Z" may be identical to or may differfrom any other moiety "Z" in the same or another molecule, so long aseach "Z" moiety conforms to one of the general formulas (II) and (III);and n represents a positive integer, which may be the same as ordifferent from the value of n for any other molecule in component (D);and in component (D) as a whole: the average value for the number of Zmoieties substituted on each phenyl ring in the polymer molecule, whichmay be referred to hereinafter as "the average value for Z moietysubstitution", is from 0.2 to 1.0; the average value of n, which may bereferred to hereinafter as "the average degree of polymerization", isfrom 2 to 50, and, because it is an average, need not be an integer,insaid composition as a whole, the aforementioned phosphoric acid ions(A), condensed phosphoric acid ions (B), oxidizing agent (C), andwater-soluble polymer (D) being present in a weight ratio(A):(B):(C):(D) of 0.1 to 30:0.1 to 10:0.1 to 10:0.1 to
 20. 2. Acomposition as defined in claim 1, wherein the oxidizing agent componentincludes at least one material selected from the group consisting ofhydrogen peroxide, chlorates, and nitrites.
 3. A composition as definedin claim 2, wherein phosphoric acid ions (A), condensed phosphoric acidions (B), oxidizing agent (C), and water-soluble polymer (D) are presentin a weight ratio (A):(B):(C):(D) of 0.5 to 5:0.5 to 3.0:2 to 5:0.5 to5.
 4. A composition as defined in claim 1, wherein phosphoric acid ions(A), condensed phosphoric acid ions (B), oxidizing agent (C), andwater-soluble polymer (D) are present in a weight ratio (A):(B):(C):(D)of 0.5 to 5:0.5 to 3.0:2 to 5:0.5 to
 5. 5. A method for the treatment ofan aluminiferous metal surface, comprising a step of bringing thealuminiferous metal surface into contact with an aqueous liquid surfacetreatment composition which contains a composition as claimed in claim 4and has a pH value not more than 6.5.
 6. A method according to claim 5,wherein the contact between the aluminiferous metal surface and theaqueous liquid surface treatment composition is maintained for a timefrom 1 to 60 seconds at a temperature from 35 to 65° C., and the surfacewhich has thus been brought into contact is rinsed with water afterdiscontinuance of the contact and is subsequently dried.
 7. A methodaccording to claim 6, wherein the dried surface formed is heated to atemperature of at least 200° C. for a time of at least 1 minute in theambient atmosphere.
 8. A method according to claim 7, wherein thesurface treatment composition has a pH from 2.0 to 6.5 andcomprises:from 1 to 30 g/l of component (A); from 0.1 to 10 g/l ofcomponent (B); from 0.1 to 10 g/l of component (C); and from 0.1 to 20g/l of component (D).
 9. A method for the treatment of an aluminiferousmetal surface, comprising a step of bringing the aluminiferous metalsurface into contact with an aqueous liquid surface treatmentcomposition which contains a composition as claimed in claim 3 and has apH value not more than 6.5.
 10. A method according to claim 9, whereinthe contact between the aluminiferous metal surface and the aqueousliquid surface treatment composition is maintained for a time from 1 to60 seconds at a temperature from 35 to 6520 C., and the surface whichhas thus been brought into contact is rinsed with water afterdiscontinuance of the contact and is subsequently dried.
 11. A methodaccording to claim 10, wherein the dried surface formed is heated to atemperature of at least 200° C. for a time of at least 1 minute in theambient atmosphere.
 12. A method according to claim 11, wherein thesurface treatment composition has a pH from 2.0 to 6.5 andcomprises:from 1 to 30 g/l of component (A); from 0.1 to 10 g/l ofcomponent (B); from 0.1 to 10 g/l of component (C); and from 0.1 to 20g/l of component (D).
 13. A method for the treatment of an aluminiferousmetal surface, comprising a step of bringing the aluminiferous metalsurface into contact with an aqueous liquid surface treatmentcomposition which contains a composition as claimed in claim 2 and has apH value not more than 6.5.
 14. A method according to claim 13, whereinthe contact between the aluminiferous metal surface and the aqueousliquid surface treatment composition is maintained for a time from 1 to60 seconds at a temperature from 35 to 65° C., and the surface which hasthus been brought into contact is rinsed with water after discontinuanceof the contact and is subsequently dried.
 15. A method according toclaim 14, wherein the dried surface formed is heated to a temperature ofat least 200° C. for a time of at least 1 minute in the ambientatmosphere.
 16. A method according to claim 15, wherein the surfacetreatment composition has a pH from 2.0 to 6.5 and comprises:from 1 to30 g/l of component (A); from 0.1 to 10 g/l of component (B); from 0.1to 10 g/l of component (C); and from 0.1 to 20 g/l of component (D). 17.A method for the treatment of an aluminiferous metal surface, comprisinga step of bringing the aluminiferous metal surface into contact with anaqueous liquid surface treatment composition which contains acomposition as claimed in claim 1 and has a pH value not more than 6.5.18. A method according to claim 17, wherein the contact between thealuminiferous metal surface and the aqueous liquid surface treatmentcomposition is maintained for a time from 1 to 60 seconds at atemperature from 35 to 65° C., and the surface which has thus beenbrought into contact is rinsed with water after discontinuance of thecontact and is subsequently dried.
 19. A method according to claim 18,wherein the dried surface formed is heated to a temperature of at least200° C. for a time of at least 1 minute in the ambient atmosphere.
 20. Amethod according to claim 19, wherein the surface treatment compositionhas a pH from 2.0 to 6.5 and comprises:from 1 to 30 g/l of component(A); from 0.1 to 10 g/l of component (B); from 0.1 to 10 g/l ofcomponent (C); and from 0.1 to 20 g/l of component (D).